There is a conventionally known color filter handling a first light ray and a second light ray. The first light ray has a uni-directional optical path in which incident light from one principal surface side of the color filter passes through the filter only once to be colored and is guided to the other principal surface side. The second light ray has a bidirectional optical path in which incident light from the other principal surface side of the color filter passes through the filter to be colored, and the transmitted light ray is reflected by a light reflective element or the like disposed on the one principal surface side to enter the filter again and pass to be colored, and returns to the other principal surface side. This color filter is used for a so-called transflective type liquid crystal display device which applies optical modulation to external light incident from the front side according to an image to be displayed, and at the same time reflects and guides the light to the front side, while applying optical modulation to the incident light from a backlight system from the rear side according to an image to be displayed likewise, and at the same time making this light to be passed and guided to the same front side. This type of liquid crystal display device effectively displays images principally using external light (ambient light) when the operating environment is bright (reflective mode) and principally using self-emitted light of the backlight system (transmissive mode) when the operating environment is dark.
Such a transflective type liquid crystal display device is disclosed in Non-Patent Document 1 etc. In this device, each pixel electrode is divided into a reflective area and a transmissive area. The reflective area is a reflective electrode part made of aluminum coated on an acrylic resin having an uneven surface, while the transmissive area is a transparent electrode part made of ITO (indium tin oxide) having a flat surface. Furthermore, the transmissive area is placed in the center of one rectangular pixel area and has a rectangular shape substantially analogous to the pixel area, while the reflective area is a part of the pixel area other than the rectangular transmissive area and has a shape surrounding this rectangular transmissive area. Such a pixel structure etc. is intended to improve legibility.
However, in this known liquid crystal display device, the transmissive area and the reflective area are different in color purity of the displayed color are though these areas are in the same pixel area. This is attributable to the fact that the light from the backlight system and the external light which have different optical paths are colored in the same way, which leads to deterioration of quality of the displayed colors over a display screen.
One such patent application of an invention to solve such a problem is Patent Document 1 filed by the same applicant as that of the present application. The color filter according to this Document is a color filter which colors first light having a uni-directional optical path and second light having a bidirectional optical path for each pixel, and which includes a first coloring part for coloring the first light and a second coloring part for coloring the second light, the first and second coloring parts having different thicknesses. Furthermore, the color filter which colors the first light having a uni-directional optical path and the second light having a bidirectional optical path for each pixel is arranged to be comprised of: a step-forming layer which can be supported by a base layer and is made of an optical transmissive material patterned so as to form at least one concave section having a bottom face of predetermined shape corresponding to an area to transmit the first light and a wall face of a predetermined height in a pixel; and a coloring layer deposited on the step-forming layer and the concave section for coloring the first and second light.
According to this, since the first coloring part and the portion of the coloring layer in the area of the bottom face can be made thicker than the portion of the coloring layer (second coloring part) in other areas, it is possible to have a relatively large coloring effect on the first light having the uni-directional optical path, namely, the first light that can be subjected to coloring effect only once, and to have a relatively small coloring effect on the second light having the bidirectional optical path, namely, the second light that can be subjected to coloring effect twice. This makes it possible to reproduce colors of the first light and second light at a uniform color purity within a pixel and thereby improve the quality of color display over the screen.    [Non-Patent Document 1]    M. Kubo, et al. ‘Development of Advanced TFT with Good Legibility under Any Intensity of Ambient Light’, IDW'99, Proceedings of The Sixth International Display Workshops, AMD3-4, page 183-186, Dec. 1, 1999, sponsored by ITE and SID    [Patent Document 1]    Japanese Patent Application Laid-Open No. 2003-84122 (particularly, see FIG. 3 and claims, and paragraphs [0009], [0010] and [0030] to [0039])